Hello _ welcome to the forum, Im sure your going to find some interesting lads here, all willing to help and dispense advice. Sorry to hear about your bike, but good that it may have led to into microlighting. Let me try and answer some of your questions though I have no doubt that others will add as needed.
My questions to your experts is though...
1- Is it worth it buying one of thgese R25k-R60K microlights on the forums, junkmail and gumtree as your first.
Yes - No problems with a trike in that price range. I wouldnt however buy it off gumtree. Preferably buy one from one of the forums and from a guy who you can track and keep in touch with. Buy one thats been looked after flown and loved buy the previous owner. Several airfields have hangars full of trikes that are just standing and rotting away, sometimes those make their way onto gomboom and im not sure thats what you want. Find something that will give you GREAT first experiences, not put you off.
2- What is the running costs (ie. how much is a service and how often is it needed.) - HMmm as memory serves its fifty hours in between services BUT that varies and the plane will have an operators manual with strict service intervals and instructions. How much to service?? also. difficult to say as it depends on the service, but would be a lot less that a superbike !! (normally)
3 -What other costs is involved in regards to inspections and safety etc - there is a yearly inspection in order to keep and renew your ATF which is an Authority to Fly, Guess the same as a bike or car registration. In order to get that done an Approved Person (certified on the plane) will have to do an inspection and that can be a few hundred rand once a year...the authority to fly is also 300?? odd rand a year - There are annnual aeroclub and Misasa fees... probably 800 bucks per year as well. a Radio license 180?? rand per annum or thereabouts. flight medical R 1000 every two years... so really pretty inexpensive
4- What does it cost to strore it in a hangar - in the region of 400 - 700 rand a month... maybe more maybe less depending on where you keep it
5- What fees is associated with airfields when i want to take a flight. _ Beer after the flight can get expensive

otherwise none. most private airfields that you hangar at will let you fly in and out as you please whenever you want. OCCASIONALLY you maybe asked to pay a landing fee at an airfield but not that often - landing fee R50 ish
in short, what will it cost me everytime i fly it and what will it cost annually (or whatever period major expenses is incurred) depending on your engine you should burn about 15 -20- litres of fuel per hour. factor in a cost of a service at 3500 / 50 hours odd gives you R 70 - add that to your fuel cost and your pretty much there. If you insure it, add that as well... but running costs per hour are affordable!!
Hope thats offered some help and good luck